NAME: Streptococcus pyogenes
SYNONYM OR CROSS REFERENCE: Group A (β-hemolytic) streptocci (GAS), streptococcal sore throat, strep throat, pharyngitis, scarlet fever, impetigo, erysipelas, puerperal fever, necrotizing fasciitis, toxic shock syndrome, septicaemia, acute rheumatic fever, acute post-streptococcal glomerulonephritis, gas gangrene
CHARACTERISTICS: Streptococcus pyogenes is an aerobic, gram-positive extracellular bacterium (1, 2). It is made up of non-motile, non-sporing cocci that are less then 2 µm in length and that form chains and large colonies greater then 0.5 mm in size (3, 4). It has a β-hemolytic growth pattern on blood agar and there are over 60 different strains of the bacterium (5, 6)
PATHOGENICITY/TOXICITY: This bacterium is responsible for a wide array of infections (7, 8). It can cause streptococcal sore throat which is characterized by fever, enlarged tonsils, tonsillar exudate, sensitive cervical lymph nodes and malaise (6, 9). If untreated, strep throat can last 7-10 days (9). Scarlet fever (pink-red rash and fever) as well as impetigo (infection of the superficial layers of skin) and pneumonia are also caused by this bacterium (3, 6, 7, 10). Septicaemia, otitis media, mastitis, sepsis, cellulitis, erysipelas, myositis, osteomyelitis, septic arthritis, meningitis, endocarditis, pericarditis, and neonatal infections are all less common infections due to S. pyogenes (3, 6, 7). Streptococcal toxic shock syndrome, acute rheumatic fever (joint inflammation, carditis and CNS complications), post-streptococcal glomerulonephritis (inflammation, hematuriia, fever, edema, hypertension, urinary sediment abnormalties and severe kidney pain) and necrotizing fasciitis (rapid and progressive infection of subcutaneous tissue, massive systematic inflammation, hemorrhagic bullae, crepitus and tissue destruction) are some of the more serious complications involving S. pyogenes infections (1, 6-8). There are at least 517,000 deaths globally each year due to severe S. pyogenes infections and rheumatic fever disease alone causes 233,000 deaths (8). 1,800 invasive S. pyogenes disease-related deaths are reported in the USA yearly, necrotizing fasciitis kills about 30% of patients and streptococcal toxic shock syndrome has a mortality rate of 30-70% (3, 11, 12).
EPIDEMIOLOGY: Different clinical manifestations of this bacterium are more common in different parts of the world. Streptococccal pharyngitits is predominant in temperate areas and peaks in late winter and early spring (5, 9). There are 616 million cases of pharyngitis caused by S. pyogenes world-wide each year (5, 8). 15-20% of school-aged children has S. pyogenes in its carrier form in their throats and are more at risk of having the disease (5, 9). Impetigo is more common with children in warm humid climates and there are 111 million reported cases world-wide each year (5). There are 115.6 million cases of rheumatic heart disease yearly and at least 18.1 million cases of invasive infections, predominantly in older populations (3, 8). Post-streptococcal glomerulonephritis is seasonal and is more common in children, young adults and males (1). Crowding and poor hygiene increase the chance of an outbreak of GAS infections (1).
INFECTIOUS DOSE: Unknown.
MODE OF TRANSMISSION: Transmission via respiratory droplets, hand contact with nasal discharge and skin contact with impetigo lesions are the most important modes of transmission (5, 9, 13). The pathogen can be found in its carrier state in the anus, vagina, skin and pharynx and contact with these surfaces can spread the infection (5, 14, 15) The bacterium can be spread to cattle and then back to humans through raw milk as well as through contaminated food sources (salads, milk, eggs); however, cattle do not contract the disease (16-18). Necrotizing fasciitis is usually because of contamination of skin lesions or wounds with the infectious agent (12).
INCUBATION PERIOD: The incubation period is usually 1-3 days (9).
COMMUNICABILITY: If untreated, patients with streptococcal pharyngitis are infective during the acute phase of the illness, usually 7-10 days, and for one week afterwards; however, if antibiotics are used, the infective period is reduced to 24 hours (9). The bacterium can remain in the body in its carrier state without causing illness in the host for weeks or months and is transmissible in this state (5).
ZOONOSIS: Cows infected by humans are intermediate hosts and can pass the bacterium in their milk, which, if consumed unpasteurized, can infect other humans (16).
DRUG SUSCEPTIBILITY: S. pyogenes infections are susceptible to a variety of drugs: β-lactams such as penicillin, as well as erythromycin, clindamycin, imipenem, rifampin, vanomycin, macrolides and lincomycin; however, certain strains of the bacterium have been found to resistant to macrolides, lincomycin, chloramphenicol, tetracyclines and cotrimoxazole (5, 7, 19, 20).
SUSCEPTIBILITY TO DISINFECTANTS: This bacteria is susceptible to 1% sodium hypochlorite, 4% formaldehyde, 2% glutaraldehyde, 70% ethanol, 70% propanol, 2% peracetic acid, 3-6% hydrogen peroxide and 0,16% iodine (2).
PHYSICAL INACTIVATION: Bacteria are susceptible to moist heat (121 ºC for at least 15 minutes) and dry heat (170 ºC for at least 1 hour) (21).
SURVIVAL OUTSIDE HOST: The bacterium can survive on a dry surface for 3 days to 6.5 months (22). It has been found to survive in ice cream (18 days), raw and pasteurized milk at 15-37 ºC (96 hrs), room temperature butter (48 hrs), and neutralized butter (12-17 days) (17). GAS has been found to last several days in cold salads at room temperature (18).
SURVEILLANCE: Monitor for symptoms. Confirm infection by bacteriological and serological testing, latex bead agglutination, fluorescent antibody staining or ELISA (6).
Note: All diagnostic methods are not necessarily available in all countries.
FIRST AID/TREATMENT: Appropriate antibiotic treatment is necessary for a S. pyogenes infection. Penicillin is used for respiratory tract infections (pharyngitis) and macrolides or lincosamides are used if there are allergies (5, 6). Clindamycin may be used in cases of necrotizing fasciitis and surgical debridement of the affected area is necessary (2, 5).
IMMUNIZATION: None (6).
PROPHYLAXIS: Administering penicillin to carriers has been shown to reduce the number of people infected during an outbreak of streptococcal sore throat (18).
LABORATORY-ACQUIRED INFECTIONS: 78 laboratory-acquired infections by streptococcal agents have been reported as of 1983 (2).
SPECIAL HAZARDS: None
RISK GROUP CLASSIFICATION: Risk group 2 (24).
CONTAINMENT REQUIREMENTS: Containment Level 2 facilities, equipment, and operational practices for work involving infectious or potentially infectious material, animals, or cultures.
PROTECTIVE CLOTHING: Lab coat. Gloves when direct skin contact with infected materials or animals is unavoidable. Eye protection must be used where there is a known or potential risk of exposure to splashes (25).
OTHER PRECAUTIONS: All procedures that may produce aerosols, or involve high concentrations or large volumes should be conducted in a biological safety cabinet (BSC) (25). The use of needles, syringes and other sharp objects should be strictly limited. Additional precautions should be considered with work involving animals or large scale activities (25).
SPILLS: Allow aerosols to settle and, wearing protective clothing, gently cover spill with paper towels and apply appropriate disinfectant, starting at the perimeter and working towards the centre. Allow sufficient contact time before clean up (25).
DISPOSAL: Decontaminate all wastes before disposal by incineration, chemical disinfection or steam sterilization (25).
STORAGE: The infectious agent should be stored in a sealed and identified container (25).
REGULATORY INFORMATION: The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.
UPDATED: July 2010
PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada.
Although the information, opinions and recommendations contained in this Pathogen Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.
Public Health Agency of Canada, 2010